Apple's having given us Time Machine doesn't negate the fact that an indeterminate percentage of the world's current and potential Mac users, you, as has been already been noted, included, has been disenfranchised and/or inconvenienced and/or forced to spend extra money for something that may, in some circumstances, be considered useless.
I've been a computer owner since 1977, when I got my first Radio Shack TRS-80, and if there's one thing I've learned in that time it's that a backup hard drive is *never* useless.
There are two kinds of computer users in the world: those who have experienced a catastrophic loss of their hard drive, and those who will. Anyone on any computer of any kind whatsoever needs to understand that if your data are important to you, a backup system is not optional. You *will* lose data if you don't have one; it's only a matter of time.
I actually keep two--one that I do frequent backups onto, so that if my hard drive takes a header I'll never lose more than a day or two's work; and one that I do less frequent backups onto, so that if I accidentally delete a critical file and I don't figure it out for a week, I'll still be able to recover it.
